Conjugated diene butyl elastomer copolymer

ABSTRACT

A heterogeneous catalytic process for dehydrohalogenating allylically halogenated olefinic hydrocarbon polymers to produce conjugated diene unsaturated polymeric products is disclosed comprising employing certain metal containing catalyst compositions, especially activated alumina supported copper containing catalysts. The process is especially suitable for the preparation of conjugated diene butyl elastomers from halogenated butyl rubber and produces products having relatively high reactivity levels in terms of active diene content.

This is a division of application Ser. No. 966,396, filed 12/4/78, now U.S. Pat. No. 4,211,855 which is a division of Ser. No. 775,389, filed 3/7/77, now U.S. Pat. No. 4,145,492.

This invention relates to the preparation of polymeric hydrocarbons having conjugated diene functionality and more particularly to a novel process for the dehydrohalogenation of allylically halogenated olefinically unsaturated hydrocarbon polymers, the halogen being chlorine or bromine.

The present invention, while developed with particular reference to the production of improved conjugated diene butyl elastomers, is applicable in its broadest sense as a means of effectively dehydrohalogenating in a heterogeneous catalytic liquid phase process any hydrocarbon composed of carbon and hydrogen and having allylic halogen, the halogen being chlorine or bromine substituted olefin functionality. Such polymers can be prepared by several methods including direct halogenation or inclusion of a suitable allylically halogenated monomer in the polymerizable compound. Generally the reaction proceeds by dehydrohalogenation as represented below ##STR1## to provide sites of conjugated diene unsaturation.

The process of the present invention is carried out at moderate temperatures of about 50° to 250° C. and in the liquid phase, the polymer being used neat or in solution or slurry. So far as applicant is aware, the prior art does not disclose the use of the catalysts defined herein in liquid phase dehydrohalogenation of allylically halogenated hydrocarbon polymers to provide conjugate diene derivatives thereof.

A wide variety of unsaturated hydrocarbon polymers may be halogenated to produce an allylically halogenated polymer suitable for use in the present invention. The halogen is preferably chlorine or bromine with chlorine particularly preferred. These polymers include homopolymers and copolymers of one or more C₄ -C₁₀ conjugated diolefins such as 1,4-polybutadiene, 1,4-polyisoprene, 1,2-polybutadiene; copolymers having a major proportion of one or more C₄ -C₈ monoolefins of the structure R-C(R₁)═CH₂ where R and R₁ may be alkyl, aryl, alkylaryl and cycloalkyl and a minor proportion of one or more C₄ -C₁₀ conjugated diolefins; block copolymers of a major proportion of one or more C₄ -C₁₀ conjugated diolefins and a minor proportion of one or more C₈ -C₁₄ vinyl aromatic hydrocarbons such as a butadiene-styrene copolymer; copolymers of one or more C₂ -C₁₈ monoolefins of the general formula R₂ CH═CH₂ where R₂ can be alkyl, aryl, alkylaryl or cycloalkyl with a minor proportion of one or more C₆ to C₁₂ non-conjugated diolefins such as terpolymers of ethylene, propylene and 1,4-hexadiene, dicyclopentadiene or 5-ethylidene-2 -norbornene.

Numerous methods are known for producing allylically halogenated unsaturated hydrocarbon polymers such as by using molecular chlorine, sulfuryl chloride, trichloromethanesulfonyl chloride and tert-butyl hypochlorine. Particular reagents for the introduction of an allylic bromine are molecular bromine, N-bromosuccinimide and 1,3-dibromo-5,5-dimethyl hydantoin.

Conjugated diene butyl elastomers are known and are described in U.S. Pat. Nos. 3,775,357 issued to Baldwin Nov. 27, 1973; 3,816,371 issued to Baldwin and Malatesta June 11, 1974; 3,852,253 issued to Malatesta Dec. 3, 1974; and in U.S. Ser. No. 465,479, filed Apr. 30, 1974.

Generally, these elastomers are copolymers consisting of from 85 to 99.5% by weight of a C₄ -C₇ isoolefin combined with 15 to 0.5% by weight of a conjugated C₄ -C₁₄ diolefin, the copolymer containing randomly distributed sites of conjugated diene unsaturation and small proportions of copolymer units with residual halogen present. The preferred method for preparing these elastomers is by dehydrohalogenation of the corresponding halogenated, that is, chlorinated or brominated, butyl rubber.

The expression "butyl rubber" is used in the rubber industry to describe copolymers made from a polymerization reaction mixture having therein from 70 to 99.5% by weight of an isoolefin which has about 4 to 7 carbon atoms, e.g. isobutylene, and about 30 to 0.5% by weight of a conjugated multiolefin having from about 4 to 14 carbon atoms, e.g. isoprene. The resulting copolymers contain 85 to 99.5% by weight of combined isoolefin and about 0.5 to 15% of combined multiolefin. The preparation of butyl rubber is described in U.S. Pat. No. 2,356,128, which is incorporated herein by reference. Butyl rubber generally has a number average molecular weight of about 5,000 to about 500,000, preferably 80,000 to about 250,000 and a Wijs Iodine No. of about 0.5 to 50, preferably 1 to 15. Low molecular weight butyl rubber is generally defined as having a Mv of 5,000 to 30,000 and 2-10 mole % unsaturation.

The polymer backbone of commercial butyl rubber is made up primarily of isobutylene units, with just a few percent of isoprene units. The isoprene units contribute the small amount of unsaturation present in butyl rubber. The basic preparative equations are represented by: ##STR2## which combine to form its main structure: ##STR3## wherein n+1 represent the number of isoolefin units incorporated in the butyl rubber, while m represents the number of diolefin units present, substantially as isolated units. The conjugated olefin loses its diene unsaturation upon its incorporation into the polymer backbone.

Thus, butyl rubber, as presently produced, contains only a small percentage of unsaturation, in the form of the single double bond associated with the isoprene residue which is incorporated more or less randomly throughout the polymer chain.

Halogenated butyl rubber has been developed in recent years and has contributed significantly to the elastomer business. A method of preparing halogenated butyl rubber is described in U.S. Pat. No. 3,099,644, which is incorporated herein by reference. Both chlorinated and brominated butyl rubber are known in the art. The formula for halogenated butyl rubber, X representing the halogen, is schematically typified by: ##STR4## where n, l and m have the same values as for butyl rubber, described above, though this structure is but one of several which can be formed, depending on the conditions of halogenation, the halogenating agent used, etc.

U.S. Pat. No. 3,775,387 teaches a semihomogeneous process for preparing conjugated diene butyl elastomers comprising contacting a solution of halogenated butyl rubber with a soluble metal carboxylate, a soluble carboxylic acid and a metal oxide or hydroxide. The complexity of this system requires the efficient removal of the major portion of these materials and precise control of reactant concentrations is required during the process itself.

U.S. Pat. No. 3,852,253 teaches a heterogeneous process for conjugated diene butyl elastomers wherein a solution of halogenated butyl rubber is contacted with a strong mineral acid salt of a Group IIA or IIB metal, e.g. calcium or zinc, at a temperature of from 100° to 220° C. This process is capable of reducing the residual halogen content to very low levels.

The present invention in its preferred embodiments provides an alternate, relatively simple, but highly effective process for producing these conjugated diene butyl (CDB) elastomers and is based on the discovery that certain metal containing catalysts can be used in carrying out the dehydrohalogenation of halogenated butyl rubber in the liquid phase and preferably in solution to provide improved CDB elastomers having a relatively high content of Diels-Alder active diene isomers.

The specific catalysts found useful in the present invention are as follows: cupric oxide (CuO), cuprous oxide (Cu₂ O), cupric chloride (CuCl₂), cupric sulfate (CuSO₄), tantalum oxide (Ta₂ O₅) and niobium oxide (Nb₂ O₅). With the exception of CuSO₄, when allylically chlorinated polymers such as chlorinated butyl rubber are used as the polymer being dehydrochlorinated, these catalysts are to be used with activated alumina as a support, the catalyst composition comprising about 0.5% to 50% by weight of catalyst and about 95.5% to 50% by weight of activated alumina as the support medium. Preferably the catalyst-support composition will contain 5 to 15% by weight such as about 10% by weight of catalyst.

It has been found, however, that when the polymer being treated is an allylically brominated hydrocarbon, such as brominated butyl rubber, that CuSO₄, Ta₂ O₅ and Nb₂ O₅ are also effective when used without the alumina support. Otherwise, an activated alumina supported catalyst is generally required for effective dehydrobromination.

The catalysts enumerated above have been found to be effective while other metal catalysts, such as zinc oxide on alumina support, do not produce desirable results. The use of activated alumina as a support is also considered critical since the copper catalysts named above were not as effective when a silicate support was used, the products exhibiting substantial inactive diene content and undesirable molecular weight loss. The particular effectiveness of copper catalysts in the present invention is considered unusual since these catalysts are generally categorized as olefin halogenation catalysts. Moreover, the effectiveness of CuCl₂ in connection with conjugated diene butyl is somewhat surprising since Malatesta in said U.S. Pat. No. 3,853,253 states that Friedel-Crafts catalysts are unsuitable in dehydrohalogenation processes. CuCl₂ is generally regarded as a Friedel-Crafts catalyst although a less active one than AlCl₃.

The preferred catalysts in the present invention are the copper oxides. While both CuO and Cu₂ O are equally effective, CuO is particularly preferred since it is readily available and, therefore, economically attractive.

The catalyst concentration used in the present invention is based on the ratio of halogen in the allylically halogenated polymer feedstock to metal in the metal-containing catalyst. This halogen to metal molar ratio, such as a Cl to Cu molar ratio, may vary from 5000:1 to 1:10 and preferably in the range of about 2500:1 to 1:1.

The process of the invention is a liquid phase dehydrohalogenation and may be crried out in bulk in the absence of solvent or in solution or slurry. In bulk, for example, the polymer could be pumped through a packed bed catalyst system. For higher molecular weight materials the process could be carried out in an extruder to provide a liquid phase in the absence of a solvent.

The process is carried out in solution by first dissolving the halogenated polymer, such as halogenated butyl rubber, in a suitable organic solvent such as a C₅ -C₈ substantially inert hydrocarbon, e.g. pentane, hexane, heptane, isoparaffinic solvents, mineral spirits, cyclohexane, toluene, benzene, xylene and mixtures thereof. Suitable concentrations are in the range of about 5-75 wt. % depending on the molecular weight of the polymer such as 5-20% for higher molecular weight materials. The powdered catalyst is added to a stirred solution and the reaction mixture is stirred and heated at a temperature of about 50° to 250° C. with typical reaction times being about 1 minute to 3 hours, preferably 45 minutes to 2 hours. Preferably the reaction temperature will be about 100° to 180° C. Pressure may be used as required to keep the solvents, when used below their boiling point. A method for HCl removal such as a nitrogen or inert gas sweep may be used to minimize diene isomerization or molecular weight degradation.

The CDB elastomers produced in accordance with the present invention will have a residual halogen content of about 0.05 to 0.9% by weight, a mole percent conjugated diene unsaturation in the range of about 0.4 to about 10 mol % and a number average molecular weight of about 8,000 to about 500,000. For lower molecular weight copolymers, that is less than 100,000, the mol % diene content is 0.4 to 10 while for polymer in excess of Mv=100,000 the range is 0.4 to about 4% diene content.

Structurally, the conjugated diene butyl elastomers produced in accordance with the present invention have been found to possess a distinct halogenated structure with respect to the residual halogen remaining after the reaction. The residual halogen in the products of the present invention has been found to be present as a primary allylic halogen, that is, the halogen is attached to a primary carbon atom. This structure is depicted below for a unit of the preferred conjugated diene butyl copolymers of the present invention derived from dehydrohalogenation of halogenated isobutylene-isoprene butyl rubber: ##STR5## where X represents a halogen and n+m represent the number of isoolefin units incorporated into the butyl rubber polymer backbone. This structure is contrasted with the halogen location in the halogenated butyl rubber prior to dehydrohalogenation which is depicted in the series of structures below, in which the halogen is always bonded to a secondary or tertiary carbon atom: ##STR6## This structural location of the residual halogen has not previously been observed in conjugated diene butyl copolymers prepared by dehydrohalogenation of halogenated butyl rubber.

More importantly, the products of the present invention have been found to contain a relatively higher proportion of Diels-Alder active conjugated diene isomeric structures. For the preferred copolymers derived from halogenated isobutylene-isoprene butyl rubber, this Diels-Alder active structure is defined as having an ultraviolet absorbance (λ max) in the range of 227 to 232 nm (nanometers) as contrasted with Diels-Alder inactive isomers having absorbance at 238 nm and higher such as 245 nm. In the present invention, highly improved products are obtained whereas of the total conjugated diene structures present at least 50% or more, preferably about 60 to 100 mole % of the conjugated diene isomers present are Diels-Alder active isomers. These structures are considered to be predominantly exo-trans cisoid isomers: ##STR7##

In contrast to this, CDB elastomers prepared according to the prior art processes as disclosed in U.S. Pat. Nos. 3,775,387 and 3,852,253 do not contain this relative proportion of Diels-Alder active diene isomers. This distinction has been confirmed by comparative data in dienophile curing reactions.

The invention is illustrated by the following examples which are not to be considered limitative of its scope.

EXAMPLE 1

This example illustrates generally the practice of the invention.

Table 1 reports a series of dehydrohalogenation reactions carried out using a 10% by weight cupric oxide-90% by weight activated alumina powdered catalyst. Both brominated and chlorinated isobutylene-isoprene butyl rubber were used in solution concentrations as indicated, the solvent was "Isopar G", a narrow cut isoparaffinic hydrocarbon solvent having a boiling point range of 155°-174° C. The brominated butyl rubber had a Mv=461,000 and a bromine content of 1.95 wt. %; the chlorinated butyl rubber had a Mv=478,000 and a chlorine content of 1.28 wt. %.

In Runs D, E and F the catalyst was added after the mixture reached the indicated reaction temperature and 0.2g activated alumina was added to remove HCl. In Run G, 10g MgO was used for this purpose and in Run H, 15g calcium naphthenate. In Run I, N₂ sweep was employed to remove HCl.

                                      TABLE 1                                      __________________________________________________________________________     DEHYDROHALOGENATION OF HALOGENATED BUTYLS WITH 10% CuO/γ Al.sub.2        O.sub.3                                                                        Run            A    B     C    D    E     F    G    H     I                    __________________________________________________________________________     Halobutyl      Br-Butyl                                                                            Cl-Butyl                                                                             Cl-Butyl                                                                            Cl-Butyl                                                                            Cl-Butyl                                                                             Cl-Butyl                                                                            Cl-Butyl                                                                            Cl-Butyl                                                                             Cl-Butyl             Polymer, g     30.0 261.0 50.1 50.1 50.1  50.1 145  50    30                   10% CuO/Al.sub.2 O.sub.3                                                                      1.35 17.23 0.20 0.20 0.20  0.20 9.5  1.44  2.0                  EA702.sup.1, g .045 0.19  0.03 0.03 0.03  0.03 0.09 0.02  0.045                (Cl)/(Cu) Molar                                                                               4.31 4.34  71.90                                                                               71.90                                                                               71.90 71.90                                                                               4.39 10    4.31                 Cement Conc., wt. %                                                                           9.64 9.64  9.64 9.64 9.64  9.64 9.80 9.64  9.64                 Rxn. Time, Min.                                                                               120  120   150  150  120   195  145  1200  75                   Rxn. Temp., °C.                                                                        143  143   143  143  155   135  143  143   143                  Product Analysis                                                               CD, Mole %     1.15 1.15  1.02 1.12 1.44  0.96 1.04 1.41  1.14                 Residual Halogen, Wt. %                                                                       0.91 0.48  0.44 0.51 0.16  0.59 0.76 0.22  0.56                 --Mv × 10.sup.-3                                                                        328  440   336  379  --    --   490  400   491                  Insolubles, Wt. %                                                                             1.0  3.8   0.0  4.4  4.4   5.5  --   --    0.3                  Cat. Eff. #Poly/#CuO/Al.sub.2 O.sub.3                                                         22.2 15.2  252  252  252   252  --   --    15.0                 Cat. Eff. #Poly/#CuO                                                                          222  152   2520 2520 2520  2520 --   --                         __________________________________________________________________________      .sup.1 EA702  a butylated hydroxy toluene antioxidant                    

EXAMPLE 2

A series of chlorinated butyl dehydrohalogenations were carried out as described below:

A 9.64% w/w solution of the same chlorinated butyl rubber as in Example I was prepared. To a jacketed reactor 403 ml of the solution was added. A 143° C. constant boiling mixture of xylene/ISOPAR G was added to heating jacket. 7.5g of CuO/γ Al₂ O₃ (powdered) and 0.045g EA702 were added to the solution. The stirred solution was heated to 143° C. and reacted for 60 minutes then the reactor was cooled, the stirring stopped and the catalyst allowed to settle overnight. The polymer solution was then decanted and a fresh quantity of solution equal to the first was added to the catalyst in the reactor and the process repeated 5 times. The product analyses are given below.

                  TABLE 2                                                          ______________________________________                                         (Cl)/(CuO) = 1.19 (molar) (initial conc.)                                      60' @ 143° C.                                                                  CD                          Cl (residual)                               Run #  Mole %    λ Max                                                                            --Mv × 10.sup.-3                                                                  Wt. %                                       ______________________________________                                         A      0.98      237-232  523      0.70                                        B      0.95      237-232  516      0.65                                        C      0.94      237-232  566      0.76                                        D      0.95      237-232  516      0.75                                        E      0.95      237-232  500      0.72                                        ______________________________________                                    

The results indicate that repeated use of the same catalyst consistently produced a high quality CDB product as indicted by the UV absorbance at 232-237 nm.

EXAMPLE 3

The chlorinated butyl rubber solution of Example 1 was treated with a series of copper cataysts, both supported and unsupported, to demonstrate the requirement that an activated alumina support medium be used with certain catalysts. As is seen by the data in the Table 3 below, for dehydrochlorination only copper sulfate is effective in the absence of activated alumina support. Thus, Runs C, F and G are examples of the invention and Runs A, B, D and E are comparative examples showing the production of elastomers having either excessive molecular weight loss or inactive Diels-Alder diene structure.

                                      TABLE 3                                      __________________________________________________________________________     Run      A    B     C      D    E    F      G                                  __________________________________________________________________________                   79% CuO/                                                                             10% CuCl.sub.2 / 10% Cu.sub.2 O                            Catalyst CuO  Silicate                                                                             γ Al.sub.2 O.sub.3                                                              CuCl.sub.2                                                                          Cu.sub.2 Cl.sub.2                                                                   γ Al.sub.2 O.sub.3                                                              CuSO.sub.4                         __________________________________________________________________________     Rxn. Temp. °C.                                                                   135  145   143    143  143  143    143                                Rxn. Time, Min.                                                                         120   60   120    180  120  150    120                                CD, Mole %                                                                              0.81 0.92   1.02  0.88 1.47 1.04    1.12                              λ Max                                                                            239 (245)                                                                           239 (245)                                                                            237 (232)                                                                             238 (245)                                                                           245 (240)                                                                           238 (232-245)                                                                         238                                Cl, Wt. %                                                                               0.67 0.42  --     0.43 0.24 --      0.43                              --Mv × 10.sup.-3                                                                  349  283   478    344  220  --     411                                Insolubles, Wt. %                                                                       1.4  1.1   5.1    4.7  0.0  --     0.0                                (Cl)/(Cu) Molar                                                                         1.71 2.0   3.9    2.0  2.0  3.86   2.0                                __________________________________________________________________________

EXAMPLE 4

A solution of the brominated butyl rubber as described in Example 1 was successfully dehydrobrominated at 150° C. at a reaction time of 1080 minutes using Ta₂ O₅ catalyst (unsupported, dried 72 hours at 160° C. in vacuum dessicator) to produce a product having a 1.20 mole % conjugated diene content, a UV absorbance (λ max.) at 238 nm, a residual bromine content of about 0.05% by weight and a Mv=415,000.

EXAMPLE 5

In this example the physical properties of a CDB prepared according to the invention with a cupric oxide-activated alumina catalyst were compared with those of a CDB prepared by the conventional zinc carboxylate process according to the method of U.S. Pat. No. 3,775,387. Both polymers were cured by a Diels-Alder crosslinking procedure using trimethylolpropanetrimethacrylate as the dienophile. Both polymers used were derived from chlorinated isobutylene-isoprene butyl rubber. The CDB prepared according to the present invention using a 10% CuO/γ Al₂ O₃ catalyst had a 1.17 mole % diene content, a residual chlorine content of 0.71 wt. % and a Mv=470,000. The prior art CDB product had 1.47 mole % conjugted diene, 0.10 wt. % chlorine and a Mv=416,000.

The point of the comparison is that the CDB of the present invention, despite its lower overall diene content and higher residual chlorine content, exhibits properties in the vulcanized state which compare favorably with the polymer prepared by the more complicated zinc carboxylate process which has a higher total diene content. It should be emphasized that polymer units containing residual chlorine cannot participate in the crosslinking reaction in the conditions employed. This indicates that the process of the present invention produces CDB polymers having a substantially higher proportion of Diels-Alder active diene functionality relative to the overall mole % diene content. The evaluations are in Table 4 below.

                  TABLE 4                                                          ______________________________________                                         Base Recipe                                                                    Parts by Weight:                                                                              CDB - 100; HAF Black - 36; Super                                               Multiflex - 52; AgeRite Resin D                                                (quinoline derivative rubber anti-                                             oxidant) - 3; Stearic Acid - 2;                                                Sunpar-2280 (paraffinic oil) - 7.5                                               Zinc                                                          CDB, Process Used                                                                               Carboxylate  CuO/Al.sub.2 O.sub.3                             ______________________________________                                         SR - 351 (trimethylol propane                                                  triacrylate)     1.75         1.75                                             Cured 30' @ 160° C.                                                     Tensile, MPa     9.96         11.02                                            Elongation, %    500          670                                              Aged 7 Days at 170° C.                                                  Tensile, MPa     6.24         6.68                                             Elongation, %    210          170                                              Aged 14 Days @ 170° C.                                                  Tensile, MPa     1.76         3.55                                             Elongation, %    235          195                                              ______________________________________                                    

EXAMPLE 6

To demonstrate the structural difference of the primary allylic halogen in the CDB polymers of the present invention with conventional halobutyl structures as depicted in the specification, an attempt was made to remove the residual halogen in the products of the invention using a system comprising zinc-2-ethylhexanoate, magnesium oxide and calcium stearate. This system readily dehydrochlorinates conventional chlorinated butyl rubber but fails to remove any residual chlorine from the CDB polymers of the present invention (Runs B, C and D). The results are in Table 5 below. All the polymers are of the isobutylene-isoprene type.

                  TABLE 5                                                          ______________________________________                                         ATTEMPTED REMOVAL OF RESIDUAL HALOGEN                                          FROM CDB PREPARED USING CuO/γ Al.sub.2 O.sub.3                           Run #            A       B       C     D                                       ______________________________________                                         HT-1068, g      30(1)   --      --    --                                       CDB, g                  30(2)   30(3) 30(4)                                    MgO (Maglite D), g                                                                             0.6     2.1     2.1   2.1                                      Zinc-2-ethylhexanoate                                                                          1.2     1.1     1.1   1.1                                      Calcium Stearate                                                                               --      0.3     0.3   0.3                                      EA702, g        --      0.02    0.02  0.02                                     Xylene, ml      300     300     300   300                                      Rxn. Temp. °C.   135°                                                                            135   135°                              Rxn. Time, min.          60      60    60                                      Product Analyses                                                               CD, mole %      1.29    0.94    1.14  1.15                                     Cl, wt. %       0.06    0.74    0.49  0.48                                     --Mv × 10.sup.3                                                                          --      519     427   483                                      Ester, mole %   --      0.016   0.00  --                                       ______________________________________                                          (1)Chlorinated butyl rubber 1.13 wt. % Cl                                      (2)0.96 mole % CD; 0.67 wt. % Cl; --Mv = 520,000                               (3)1.15 mole % CD; 0.48 wt. % Cl; --Mv = 440,000                               (4)Repeat of 3 but zinc salt added after reactor heated to 135° C.

EXAMPLE 7

The CDB elastomers prepared in accordance with the present invention were subjected to cure study and oven aging tests to evaluate the resistance of the product to thermal-oxidative degradation both in the vulcanized and bulk states. The purposes were to compare the products of the invention with those prepared by the prior art zinc carboxylate process of U.S. Pat. No. 3,775,387 and to evaluate the effect of residual quantity of metal catalyst, especially copper catalysts, on the thermal aging properties of the polymer, the latter being of particular importance since it is well known that free copper in a high molecular weight polymer can act as an oxidation catalyst.

The data set forth in Tables 6, 7 and 8 show that thd CDB polymers of the present invention exhibit excellent resistance to thermal oxidative degradation and are equivalent to those prepared by the zinc carboxylate method, notwithstanding the difference in conjugated diene and residual chlorine content and the presence of residual amounts of copper catalyst, one CDB containing 13 ppm of copper (as CuO/Al₂ O₃). Free copper salts on the other hand may reduce the resistance to thermal degradation.

In Table 6 dienophile and sulfur cures were carried out. The zinc carboxylate CDB dienophile returned a small advantage in elongation during aging and a smaller change in Shore A hardness, while the samples of the present invention showed slightly higher tensile strengths and moduli reflected in higher crosslink densities (lower cyclohexane swell).

In Table 7 the results of a 21-day aging test at 121° C. for sulfur-Santocure NS vulcanizates is reported. The aging results show that compound 2, a product of the invention, retained higher tensile and modulus values but a slightly greater loss of elongation and increased hardness.

Dienophile cure data is presented in Table 8 using trimethylolpropane-trimethacrylate as the curing agent. Compound 3, a product of the invention, displayed the highest original tensile and elongation. On aging the tensile advantage was retained but compounds 1 and 2 had better elongation retention. At 14 days compound 3 still possessed a (TE)_(c) value, critical tensile-elongation product, greater than the acceptable practical minimum of 3.45 MPa and 100% elongation. None of the other compounds could be considered useful at 14 days.

                                      TABLE 6                                      __________________________________________________________________________     Aging Studies - Sulfur Santocure NS and - Trimethylolpropanetriacrylate        Systems                                                                        Compound, phr   A      B      C      D                                         __________________________________________________________________________     CDB.sup.1      100    --     100    --                                         CDB.sup.2      --     100    --     100                                        Philblack N330 36     36     36     36                                         Super Multiflex                                                                               52     52     52     52                                         Age Rite Resin D.sup.3                                                                        2      2      2      2                                          Stearic Acid   2      2      2      2                                          Sunpar 2280    7.5    7.5    7.5    7.5                                        Zinc Oxide     5      5      --     --                                         Sulfur         1      1      --     --                                         Santocure NS   2      2      --     --                                         TMPTA (SR351)  --     --     1.75   1.75                                       Original Physical Properties                                                   Cure time, min.                                                                               60     60     15     15                                         Cure temp. °C.                                                                         153    153    120    120                                        Tensile, MPa   12.69  12.93  12.23  11.79                                      Elongation, %  490    505    670    600                                        Mod. @ 300%, MPa                                                                              6.07   6.61   3.38   4.82                                       Shore A        55     60     52     54                                         Swell Ratio/Wt. % Solubles in                                                  Cyclohexane    2.80/2.76                                                                             2.85/4.54                                                                             3.19/4.57                                                                             2.77/4.74                                  Cure time, min.                                                                               30     30     30     30                                         Cure temp. °C.                                                                         160    160    160    160                                        Tensile, MPa   11.92  12.30  11.89  9.96                                       Elongation, %  540    545    540    455                                        Mod. @ 300%, MPa                                                                              4.41   4.93   5.24   5.62                                       Shore A        54     54     54     55                                         Swell Ratio/Wt. % Solubles                                                                    3.08/5.45                                                                             3.01/48.7                                                                             3.04/5.13                                                                             2.78/4.93                                  Cure time, min.              60     60                                         Cure temp. °C.        160    160                                        Tensile, MPa                 9.76   9.79                                       Elongation, %                390    370                                        Mod. @ 300%, MPa             6.96   7.48                                       Shore A                      56     57                                         Swell Ratio/Wt. % Solubles   2.77/3.55                                                                             2.72/5.58                                  Aged Physical Properties                                                       Cure Identification                                                                           60' @ 153° C.                                                                  60' @ 153° C.                                                                  15' @ 160° C.                                                                  15' @ 160° C.                       Days Aged at °C.                                                                       7/121° C.                                                                      7/121° C.                                                                      7/170° C.                                                                      7/170° C.                           Tensile, MPa   6.83   7.24   7.52   6.52                                       Elongation, %  415    455    155    205                                        Mod. @ 100%, MPa                                                                              1.83   2.03   4.79   3.10                                       Mod. @ 300%, MPa                                                                              4.93   5.27   --     --                                         Shore A        60     60     70     65                                         Swell Ratio/Wt. % Solubles                                                                    --     --     1.49/3.62                                                                             1.50/3.03                                  Cure Identification                                                                           30' @ 160° C.                                                                  30' @ 160° C.                                                                  30' @ 160° C.                                                                  30' @ 160°  C.                      Days Aged at °C.                                                                       7/121° C.                                                                      7/121° C.                                                                      7/170° C.                                                                      7/170° C.                           Tensile, MPa   7.58   7.34   6.90   6.62                                       Elongation, %  370    410    145    200                                        Mod. @ 100%, MPa                                                                              2.21   1.93   4.76   3.28                                       Mod. @ 300%, MPa                                                                              6.24   5.52   --     --                                         Shore A        64     64     70     66                                         Swell Ratio/Wt. % Solubles                                                                    --     --     1.48/3.64                                                                             1.63/4.73                                  Cure Identification                                                                           --     --     60/160 60/160                                     Days Aged at °C.                                                                       --     --     7/170  7/170                                      Swell Ratio/Wt. % Solubles                                                                    --     --     1.53/3.88                                                                             1.58/3.52                                  __________________________________________________________________________      .sup.1 CuO/δ Al.sub.2 O.sub.3 CDB CD = 1.18 mole % Insol. = 2.7 wt.      % Cl = 0.54 wt. % --Mv = 395,000 Cu = 13 ppm (as CuO/δ Al.sub.2          O.sub.3)                                                                       .sup.2 Zn(O.sub.2 CR).sub.2 CDB CD = 1.47 mole % Cl = 0.10 wt. % --Mv =        416,000                                                                        .sup.3 poly  2,2,4trimethyl-1,2,dihydroquinoline                         

                                      TABLE 7                                      __________________________________________________________________________     COMPARISON OF                                                                  UNAGED AND AGED SULFUR CURED CDB VULCANIZATES                                  __________________________________________________________________________     Compound, phr    1        2        3                                           __________________________________________________________________________     CDB.sup.1        --       100      100                                         CDB.sup.2        100      --       --                                          Philblack, N330  36       36       36                                          Flextol R.sup.4  2.0      2.0      2.0                                         DuPont DMD.sup.3 --       --       1.0                                         Protox (ZnO) 166 5.0      5.0      5.0                                         Super Multiflex  52       52       52                                          Stearic Acid     --       2.0      2.0                                         Sunpar 2280      7.5      7.5      7.5                                         Sulfur           2.0      2.0      2.0                                         Santocure NS     1.0      1.0      1.0                                         Original Physical Properties                                                   Cured min. @ 153° C.                                                                  15 30 60 15 30 60 15 30 60                                       Tensile, MPa  12.00                                                                             11.86                                                                             11.62                                                                             8.27                                                                              11.76                                                                             12.41                                                                             11.17                                                                             11.62                                                                             12.38                                    Elongation, % 605                                                                               505                                                                               440                                                                               650                                                                               450                                                                               435                                                                               555                                                                               525                                                                               465                                      300% Mod., MPa                                                                               5.00                                                                              5.86                                                                              6.48                                                                              2.45                                                                              5.69                                                                              6.55                                                                              4.65                                                                              5.58                                                                              7.17                                     Shore A       55 60 62 55 56 60 58 60 65                                       Swell Ratio/Wt. % Solubles                                                                   3.20/                                                                             2.82/                                                                             2.73/                                                                             3.92/                                                                             2.88/                                                                             2.70/                                                                             2.95/                                                                             2.73/                                                                             2.65/                                    in Cyclohexane                                                                               5.62                                                                              4.86                                                                              5.02                                                                              6.06                                                                              4.72                                                                              4.70                                                                              5.84                                                                              5.56                                                                              5.41                                     __________________________________________________________________________     Compound         1        2        3                                           __________________________________________________________________________     Aged Physical Properties                                                       Cure Conditions        15' @ 153° C.                                    Days Aged @ 121° C.                                                                   7  14 21 7  14 21 7  14 21                                       Tensile, MPa  8.45                                                                              6.14                                                                              5.55                                                                              9.00                                                                              6.41                                                                              6.96                                                                              7.93                                                                              7.14                                                                              6.45                                     Elongation, % 380                                                                               350                                                                               335                                                                               270                                                                               280                                                                               260                                                                               290                                                                               300                                                                               270                                      Shore A       64 60 64 68 66 66 74 70 70                                       Cure Conditions        20' @ 153° C.                                    Tensile, MPa  8.10                                                                              6.34                                                                              5.10                                                                              8.76                                                                              7.00                                                                              6.72                                                                              8.34                                                                              6.90                                                                              6.31                                     Elongation, % 395                                                                               345                                                                               310                                                                               295                                                                               300                                                                               270                                                                               305                                                                               305                                                                               285                                      Shore A       65 65 65 69 68 68 72 70 68                                       Cure Conditions        60' @ 153°  C.                                   Tensile, MPa  8.10                                                                              6.34                                                                              6.10                                                                              8.27                                                                              6.72                                                                              6.79                                                                              8.14                                                                              6.41                                                                              6.03                                     Elongation, % 395                                                                               345                                                                               365                                                                               310                                                                               305                                                                               310                                                                               310                                                                               295                                                                               300                                      Shore A       68 65 65 68 65 70 72 66 70                                       __________________________________________________________________________      .sup.1 CuO/γ Al.sub.2 O.sub.3 CDB Cu = 1.13 mole %, M.sub.v =            383,000 Insolubles  2.4 wt. % Cl = 0.51 wt. %; Cu 13 ppm (as CuO/γ       Al.sub.2 O.sub.3)                                                              .sup.2 Zn(O.sub.2 CR).sub.2 CD = 1.47 mole %, M.sub.v = 416,000 Cl = 0.10      wt. %                                                                          .sup.3 DuPont DMD N,N' Disalicylidene  1,2 propane diamine                     .sup.4 Flectol H Purified form of                                              poly2,2,4-trimethyl-1,2-dihydroquinoline-                                

                                      TABLE 8                                      __________________________________________________________________________     COMPARISON OF UNAGED AND AGED DIENOPHILE                                       CURED CONJUGATED DIENE BUTYLS                                                  __________________________________________________________________________     Masterbatch            A         B                                             __________________________________________________________________________             CDB.sup.1      --        100                                                   CDB.sup.2      100       --                                                    Philblack N330 36        36                                                    Super Multiflex                                                                               52        52                                                    Age Rite Resin D                                                                              2.0       2.0                                                   Stearic Acid   2.0       2.0                                                   Sunpar 2280    7.5       7.5                                           __________________________________________________________________________     Compound          1         2         3    4                                   __________________________________________________________________________             Masterbatch A                                                                            199       199       --   --                                          Masterbatch B                                                                            --        --        199  199                                         DuPont DMD.sup.3                                                                         --         1        --   1                                           SR-351 (TMPTA).sup.4                                                                     1.75      1.75      1.75 1.75                                        Cure 30' @ 160° C.                                              __________________________________________________________________________     Unaged and Aged Physical Properties                                            __________________________________________________________________________     Days at 170° C.                                                                     0  7  14 0  7  14 0  7  14 0  7  14                                Tensile, MPa                                                                               9.93                                                                              6.24                                                                              1.76                                                                              9.93                                                                              5.45                                                                              1.14                                                                              11.03                                                                             6.69                                                                              3.55                                                                              7.14                                                                              4.17                                                                              1.93                              Elongation, %                                                                              500                                                                               210                                                                               235                                                                               470                                                                               205                                                                               270                                                                               670                                                                               170                                                                               195                                                                               280                                                                               140                                                                               175                               Modulus @ 100%, MPa                                                                        0.93                                                                              2.65                                                                              0.72                                                                              1.07                                                                              2.38                                                                              0.41                                                                              0.66                                                                              3.86                                                                              1.79                                                                              1.34                                                                              3.03                                                                              1.24                              Shore A     47 65 55 49 64 53 45 67 62 52 66 61                                __________________________________________________________________________      .sup.1 CuO/δ Al.sub.2 O.sub.3 CDB CD = 1.17 mole %; M.sub.v =            470,000; Insolubles = 3.5 wt. %; Cu = 13ppm (as CuO/δ Al.sub.2           O.sub.3)                                                                       .sup.2 Zn(O.sub.2 CR).sub.2 CDB CD = 1.47 mole %; M.sub.v = 416,000            .sup.3 DMD = N,N' Disalicylidene  1,2 propane diamine                          .sup.4 Trimethylolpropanetriacrylate                                      

What is claimed is:
 1. A conjugated diene butyl elastomer copolymer, said copolymer consisting of 85 to 99.5% by weight of a C₄ -C₇ isoolefin combined with 15 to 0.5% by weight of a conjugated C₄ -C₁₄ diolefin, the copolymer having randomly distributed sites of conjugated diene unsaturation and a residual halogen content of 0.05 to 0.9% by weight, the halogen being present as primary allylic halogen, at least 50 mole % of said conjugated diene unsaturation being Diels-Alder active conjugated diene units.
 2. The copolymer of claim 1 wherein the isoolefin is isobutylene and the diolefin is isoprene.
 3. The copolymer of claim 1 wherein the residual halogen is chlorine.
 4. The copolymer of claim 1 wherein the residual halogen is bromine. 